One way to open, read, write and close files

[trishankkarthik]

Presently, we have many ways to open, read, write and close files. Sometimes we use the Python built-in functions, and sometimes else we use our own file-like objects.

This makes it harder to easily adapt the code to changing requirements. (For example, I cannot easily add code to compress or decompress files and assume that it will work everywhere.)

I think we should design one file-like object to serve our needs and use that everywhere in the code.

[trishankkarthik]

#139 was due to this issue.

[lukpueh]

• TempFile doesn't behave like a Python file object secure-systems-lab/securesystemslib#180 (comment) advocates for not having a custom File-not-file class.
• Remove uses of securesystemslib.util.TempFile #918 and Remove securesystemslib.util.TempFile secure-systems-lab/securesystemslib#181 removes TUF's custom file-like TempFile implementation, and adds a single persist_temp_file utility function.
• Implement TAP 10 #485 removes native support for compressed top-level metadata (tap 10).

Let's close due to inactivity.